Conventionally, a gas barrier film having a thin film (that is, gas barrier layer) containing metal oxide such as aluminum oxide, magnesium oxide, or silicon oxide formed on the surface of a plastic substrate or a film has been used for an application in packaging products in the field of food products, pharmaceutical products, or the like. By using a gas barrier film, degradation of a product caused by water vapor or gas like oxygen can be prevented.
Recently, a gas barrier film for preventing permeation of water vapor, oxygen, or the like is also used in the field of an electronic device such as a liquid crystal display (LCD) device, a photovoltaic (PV) cell, and an organic electroluminescence (EL). For an application of the gas barrier film to an electronic device, it is required to have flexibility, transparency, heat resistance, or the like. It is also required to have a high gas barrier property, for example, a gas barrier property comparable to a glass base.
As a method for producing such a gas barrier film, mainly, a method of forming a gas barrier layer on a base such as a film by a plasma CVD method (Chemical Vapor Deposition: chemical vapor phase growth method, chemical vapor deposition method) in which metal is vapor-deposited, a vacuum vapor deposition method in which metal is vaporized by using semiconductor laser or the like and deposited on a substrate in the presence of oxygen, a method of forming a gas barrier layer by sputtering, a method of forming a gas barrier layer by coating on a base a coating liquid that has polysilazane as the main component, and then performing a surface treatment, or a method using the above methods in combination, has been known.
However, in the gas barrier layer formed by these production methods, micropores may be generated due to the protrusion present on a base surface or due to the contamination by foreign substances in the gas barrier layer. Further, tiny cracks and the like may be generated due to the expansion and contraction of the gas barrier layer. Further, scratches may be caused by bending or contacting during handling, and the like. In a gas barrier layer in which these defects have been generated, gas may pass through the defect spots, and thus the gases cannot be completely cut off.
Under the circumstances, studies have been made on a gas barrier film having a high gas barrier property, which can be desirably used for an electronic device.
In Patent Literature 1, a gas barrier film having a resin base, a first silica film derived from polysilazane, which is formed by coating on the resin base followed by irradiation with ultraviolet rays having wavelength of 155 nm to 274 nm, and a second silica film derived from colloidal silica, which is laminated on the first silica film, is disclosed. According to Patent Literature 1, it is described that the gas barrier film has excellent water vapor permeability.
The method for producing the gas barrier film mentioned above includes, a step of forming a polysilazane layer by coating a polysilazane solution on a resin base followed by drying, a step of preparing a first silica film derived from polysilazane by irradiation of the polysilazane layer with ultraviolet rays with wavelength of 155 nm to 274 nm, a step of forming a colloidal silica layer by coating a colloidal silica solution on the first silica film, and a step of forming a second silica film by drying the colloidal silica layer. In Patent Literature 1, it is described that the production cost can be reduced and productivity can be improved with the method for producing a gas barrier film described above.